[carise]

Algorithms/data structures classes are a good start.

I hear that the Coursera algorithms classes by Prof Sedgwick (Princeton) and Prof Roughgarden (Stanford) are very good. I think the Princeton ones might not be available after the Coursera switchover so would recommend downloading the course content if you can. There were some threads on HN in the last week about it.

Also MIT OpenCourseware has Intro to Algorithms which I hear is good too.

[umbs]

I viewed classes from all three mentioned above and found Prof Sedwick's classes to be very structured and to my style/liking. Prof. Roughgarden is "free flowing" and may require fast thinking to follow him. Prof Demaine's classes gets very mathematical and I found myself sometimes lost in Greek symbols. But Prof. Demaine is very thorough in building the theory.

[1] Prof Sedwick: https://www.coursera.org/course/algs4partI

As @carise said, the content may be gone after June 30th and if you want to download, you can do so using coursera-dl tool

https://github.com/coursera-dl/coursera-dl

[2] Prof Roughgarden: https://www.coursera.org/learn/algorithm-design-analysis

[3] Prof Erik Demaine (MIT OpenCourseware): https://www.youtube.com/playlist?list=PLUl4u3cNGP61Oq3tWYp6V...

There are videos of MIT's Prof Erik Demaine's Intro to Algo's from various semesters. I think any one should do.